With respect to a method of controlling a step motor, in order to reduce the electric power consumption at the rotation and halting of the step motor, a series of pulses comprising a driving voltage and a holding voltage are successively applied to a plurality of stator coils. The driving voltage is a voltage for rotating the rotor, and the holding voltage is a voltage for holding the rotor at a halted state by a voltage lower than the driving voltage.
In the prior art method of controlling a step motor as described above, however, when the driving voltage is applied to the final magnetization phase, the rotor repeats damped oscillations at the neighbourhood of a predetermined halted position due to its inertia, and when the voltage applied to the final magnetization phase is switched to the holding voltage in that state, the rotor does not follow the voltage due to its weight, and it is not halted at a predetermined halted position accurately.
As another prior art there is a high efficiency driving circuit for electric pulse motor, which is recited in U.S. Pat. No. 3,746,959.